1. Field to which the Invention Belongs
The present invention relates to a technology of estimating lifetime of piping parts in a process plant, and a technology of forming a replacing work plan of piping parts using a result of the lifetime estimation.
2. Prior Arts
As disclosed in Japanese Application Patent Laid-Open Publication No. Hei 8-178172 titled “a method of calculating and evaluating wall-thickness thinning of a component and piping system caused by erosion-corrosion” and U.S. Pat. No. 4,935,195 titled “corrosion-erosion trend monitoring and diagnostic system”, a conventional maintenance form of a process plant is that a maximum progressed value of pipe wall-thickness thinning for each of the piping parts is predicted by forming a wall-thickness estimation formula using various kinds of information necessary for wall-thickness control, particularly a wall-thickness measurement database and a document database (temperature, pressure, dissolved oxygen concentration, flow speed of the fluid flowing inside the pipe). Further, an inspection plan and a replacing work plan are made for each of the estimated piping parts.
In the conventional technology, by focusing only on an individual piping part such as one elbow or one straight pipe, the wall-thickness thinning prediction has been performed based on past wall-thickness thinning measured data. However, neither of the three-dimensional layout of the part nor the kind and the shape of a part adjacently connected to the part has been taken into consideration.
Because the piping parts (piping such as the elbow, straight pipe, reducing pipe, branch pipe and so on, as well as the valve, pump and so on) composing a process plant are disposed differently in three-dimension even if they are the same kind of parts, have the same shape and are made of the material, behavior of the fluid flowing through the parts is substantially different depending on a position where the parts are disposed and on a kind of a part to which the part is connected.
Therefore, The wall-thickness thinning rate of the piping part is varied depending on the behavior of the fluid flow. Further, durability of a plant part composing the process plant is different depending on the three-dimensional layout of the plant part and on a kind of a part to which the plant part is connected, and also depending on a condition of the fluid flowing inside the plant part and on number of plant shutdowns.
Therefore, the prior art can not have performed wall-thickness thinning prediction which takes into consideration change in the behavior of the fluid flowing through the whole pipe lines composing the process plant, and can not make an efficient plan for replacing the piping parts based on the prediction result.
Further, the prior art can not have performed wall-thickness thinning prediction on a unmeasured part even within one pipe, and can not have performed lifetime prediction of piping parts and wall-thickness thinning prediction of piping parts composing the whole process plant.
Further, in a conventional plan of replacing parts, in a case where replacing periods of the piping parts are different from one another, the piping part replacing work must be frequently performed for the replacing work corresponding to each of the piping parts. Accordingly, since each time of the replacing work needs preparation associated to the work and shutdown of the plant operation, there will occur an economical loss caused by a large cost spent in the preparation and reduction of operability associated with the plant shutdown if the repairing work often occurs.
This is due to the fact that the lifetime of piping parts of the whole process plant has not been accurately known when the replacing work plan using lifetime estimation and wall-thickness thinning estimation of parts such as pipes composing the process plant is made.